Methods of forming nitrogen-containing masses, silicon nitride layers, and capacitor constructions

ABSTRACT

The invention encompasses a method of forming a silicon nitride layer. A substrate is provided which comprises a first mass and a second mass. The first mass comprises silicon and the second mass comprises silicon oxide. A sacrificial layer is formed over the first mass. While the sacrificial layer is over the first mass, a nitrogen-containing material is formed across the second mass. After the nitrogen-containing material is formed, the sacrificial layer is removed. Subsequently, a silicon nitride layer is formed to extend across the first and second masses, with the silicon nitride layer being over the nitrogen-containing material. Also, a conductivity-enhancing dopant is provided within the first mass. The invention also pertains to methods of forming capacitor constructions.

RELATED PATENT DATA

This patent resulted from a continuation of U.S. patent application Ser.No. 09/823,200, which was filed Mar. 29, 2001, and which issued as U.S.Pat. No. 6,158,177 on Feb. 11, 2003.

TECHNICAL FIELD

The invention pertains to methods of forming nitrogen-containing massesand silicon nitride layers. The invention also pertains to methods offorming capacitor constructions.

BACKGROUND OF THE INVENTION

Silicon nitride is commonly utilized as an insulative material duringsemiconductor device fabrication. For instance, silicon nitride can beutilized as a dielectric material in capacitor constructions. Anotheruse for silicon nitride in semiconductor device fabrication is as abarrier layer to impede migration of, for example, oxygen, hydrogen, andmetallic materials.

It can be desired to simultaneously deposit silicon nitride over aconductively-doped silicon material and a silicon oxide. For instance,it can be desired to deposit silicon nitride over conductively-dopedpolycrystalline silicon to form an insulative material over thepolycrystalline silicon, and to simultaneously deposit the siliconnitride over borophosphosilicate glass (BPSG) to form a barrier layerover the BPSG.

A difficulty that can occur during such simultaneous deposition ofsilicon nitride is that the silicon nitride can form much more rapidlyover the polycrystalline silicon than over the BPSG. Specifically, anucleation rate of silicon nitride on silicon is typically significantlyhigher than it is on silicon oxides. Accordingly, the silicon nitridethickness over the polycrystalline silicon will be much thicker thanthat over the silicon oxide. For instance, a 50 Å thick silicon nitridelayer can be formed on hemispherical grain polysilicon in about the timethat it takes to grow a 20 Å thick silicon nitride layer on BPSG. The 20Å thick silicon nitride layer may not be sufficient to be a suitablebarrier layer to subsequent penetration of undesirable materials throughthe silicon nitride and into the BPSG. If materials penetrate into theBPSG, they can subsequently penetrate through the BPSG and to anunderlying active region, which can ultimately cause failure of devicesformed relative to the active region.

One solution to the above-described difficulty is to grow a thickerlayer of silicon nitride on the polycrystalline silicon to enable asufficiently thick barrier layer to be formed on the BPSG. However, suchcan result in too thick of a silicon nitride layer being deposited onthe polycrystalline silicon for later use as a dielectric material in acapacitor device. It would be desirable to develop methodology wherebysilicon nitride can be simultaneously deposited over a silicon oxide anda conductively-doped silicon material, with the deposition rate beingsubstantially the same over both the silicon oxide-containing materialand the conductively-doped silicon material.

SUMMARY OF THE INVENTION

In one aspect, the invention encompasses a method of forming anitrogen-containing mass. A substrate is provided, and the substratecomprises a silicon-containing mass and a silicon oxide-containing mass.The silicon-containing mass has substantially no oxygen therein. A firstnitrogen-containing mass is formed to be across the siliconoxide-containing mass and not across the silicon-containing mass. Afterthe first nitrogen-containing mass is formed, a secondnitrogen-containing mass is formed to extend across thesilicon-containing mass and across the silicon oxide-containing mass,with the second nitrogen-containing mass being over the firstnitrogen-containing mass.

In another aspect, the invention encompasses a method of forming asilicon nitride layer. A substrate is provided which comprises a firstmass and a second mass. The first mass comprises silicon and the secondmass comprises silicon oxide. A sacrificial layer is formed over thefirst mass. While the sacrificial layer is over the first mass, anitrogen-containing material is formed across the second mass. After thenitrogen-containing material is formed, the sacrificial layer isremoved. Subsequently, a silicon nitride layer is formed to extendacross the first and second masses, with the silicon nitride layer beingover the nitrogen-containing material. Also, a conductivity-enhancingdopant is provided within the first mass.

In yet another aspect, the invention pertains to methods of formingcapacitor constructions.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is a diagrammatic, cross-sectional view of a semiconductor waferfragment at a preliminary processing step of a method of the presentinvention.

FIG. 2 is a view of the FIG. 1 wafer fragment shown at a processing stepsubsequent to that of FIG. 1.

FIG. 3 is a view of the FIG. 1 wafer fragment shown at a processing stepsubsequent to that of FIG. 2.

FIG. 4 is a view of the FIG. 1 wafer fragment shown at a processing stepsubsequent to that of FIG. 3.

FIG. 5 is a view of the FIG. 1 wafer fragment shown at a processing stepsubsequent to that of FIG. 4.

FIG. 6 is a view of the FIG. 1 wafer fragment shown at a processing stepsubsequent to that of FIG. 5.

FIG. 7 is a view of the FIG. 1 wafer fragment shown at a processing stepsubsequent to that of FIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws “to promote the progressof science and useful arts” (Article 1, Section 8).

An exemplary process of the present invention is described withreference to FIGS. 1–7. Referring initially to FIG. 1, a semiconductorwafer fragment 10 is illustrated at a preliminary processing step of amethod of the present invention. Wafer fragment 10 includes a substrate12. Substrate 12 can comprise, for example, monocrystalline siliconlightly doped with p-type background dopant. To aid in interpretation ofthe claims that follow, the terms “semiconductive substrate” and“semiconductor substrate” are defined to mean any constructioncomprising semiconductive material, including, but not limited to, bulksemiconductive materials such as a semiconductive wafer (either alone orin assemblies comprising other materials thereon), and semiconductivematerial layers (either alone or in assemblies comprising othermaterials). The term “substrate” refers to any supporting structure,including, but not limited to, the semiconductive substrates describedabove.

A pair of wordlines 14 and 16 are supported by substrate 12. Wordline 16is provided on an isolation region 18 which can comprise, for example, ashallow trench isolation region of silicon dioxide. Wordline 14 has apair of source/drain regions 18 and 20 provided adjacent thereto, andfunctions as a transistor gate to gatedly couple source/drain regions 18and 20 with one another. Source/drain regions 18 and 20 can comprise,for example, n-type or p-type doped regions of semiconductive substrate12. Source/drain regions 18 and 20 would typically be heavily-doped(with the term “heavily-doped” referring to a dopant concentration of atleast 10¹⁹ atoms/cm³). Also shown in FIG. 1 are lightly-dopedsource/drain regions 22 and 24 (with the term “lightly-doped” referringto a source/drain region having a dopant concentration of less than 10¹⁹atoms/cm³) which extend from wordline 14 to heavily-doped regions 18 and20. Regions 22 and 24 can comprise either n-type dopant or p-typedopant.

Wordlines 14 and 16 comprise layers 26, 28, 30 and 32 patterned intostacks. Layer 26 is a pad oxide, and typically comprises silicondioxide; layer 28 typically comprises conductively-doped silicon, suchas, for example, conductively-doped polycrystalline silicon; layer 30typically comprises metal silicide, such as, for example, tungstensilicide or titanium silicide; and layer 32 typically comprises aninsulative cap, such as, for example, silicon nitride.

A pair of sidewall spacers 34 are formed along sidewalls of wordline 14,and a pair of sidewall spacers 36 are formed along sidewalls of wordline16. The sidewall spacers can comprise, for example, silicon nitride.

An insulative mass 40 is formed over substrate 12, and over wordlines 14and 16. Mass 40 can comprise a silicon oxide, such as, for example,BPSG. Accordingly, mass 40 can be considered a silicon oxide-containingmask. Mass 40 has an upper surface 41.

An opening 42 is formed within mass 40 and extends to source/drainregion 20. Opening 42 can be formed by, for example, providing apatterned photoresist mask (not shown) over insulative mass 40, andsubsequently etching mass 40 to transfer a pattern from the patternedphotoresist mask to mass 40. Subsequently, the photoresist mask can beremoved.

A semiconductive material 44 is provided over mass 40 and within opening42. Semiconductive material 44 can, for example, comprise silicon,consist essentially of silicon, consist essentially ofconductively-doped silicon, or consist of conductively-doped silicon. Inthe shown embodiment, semiconductive material 44 has a roughened surface46, and accordingly can correspond to rugged polycrystalline silicon,such as, for example, to hemispherical grain polysilicon.

Semiconductive material 44 is ultimately doped withconductivity-enhancing dopant to transform semiconductive material 44into a conductive material. Such doping can occur in situ duringformation of semiconductive material 44, or can occur subsequent toformation of semiconductive material 44 by, for example, ionimplantation.

Semiconductive material 44 can be a silicon-containing mass havingsubstantially no oxygen therein. It is noted that if semiconductivematerial 44 is a silicon-containing mass, there can be a thin layer ofnative oxide (not shown) that forms over layer 44 if layer 44 is exposedto an oxygen ambient. Even if such thin layer of native oxide forms overlayer 44, layer 44 is still considered to have substantially no oxygentherein because the majority of the oxygen will be associated with asurface of layer 44 rather than extending into layer 44. Since there canbe a small amount of oxygen that penetrates the upper surface of layer44 during formation of native oxide across such upper surface, the term“substantially no oxygen” is utilized instead of saying that there isabsolutely no oxygen within layer 44 in recognition of such small amountof oxygen that can penetrate material 44 during formation of silicondioxide across a surface of material 44. However, even if a layer ofsilicon dioxide is over mass 44, the bulk of mass 44 can remainnon-oxidized and can accordingly be considered to correspond to anon-oxidized silicon-containing mass.

A distinction between mass 44 and silicon dioxide mass 40 is that therewill be a difference in a rate of silicon nitride formation over mass 44relative to mass 40 if conventional methods are utilized for growingsilicon nitride simultaneously over the material of mass 44 and thematerial of mass 40.

If desired, silicon-containing mass 44 can be treated with nitrogen toalleviate or prevent native oxide growth. For instance, anitrogen-containing layer (not shown) can be formed over mass 44 byexposing the mass to ammonia at a temperature of from about 300° C. toabout 900° C. and a pressure of from about 2 mTorr to about 1 atmospherefor a time of from about 30 seconds to about 60 minutes, to form thenitrogen layer to a thickness of less than about 10 Å. Suitablemethodology can include thermal methods and/or plasma assisted methods.Preferably, the nitrogen layer will be formed to a thickness of fromabout 5 Å to about 10 Å, with a monolayer of the nitrogen-comprisinglayer being most preferred. The nitrogen-comprising layer will typicallybe silicon nitride. A preferred pressure for forming thenitrogen-comprising layer can be from about 1 Torr to about 10 Torr.

Referring to FIG. 2, a sacrificial layer 50 is formed within opening 42and over a portion of mass 44 that extends within such opening.Sacrificial material 50 can comprise, for example, photoresist, and canbe formed by providing a layer of photoresist across an entirety of anupper surface of wafer fragment 10, and subsequentlyphotolithographically patterning the photoresist to leave only a portionof the photoresist remaining within opening 42. Alternatively, thephotoresist can be removed by chemical-mechanical polishing.

Photoresist 50 is shown having an upper surface 52 that is elevationallylower than upper surface 41 of insulative mass 40. It is noted that suchis an exemplary application of the present invention, and that otherapplications are encompassed by the present invention wherein uppersurface 52 is at the same elevational height as upper surface 41, or isabove the elevational height of upper surface 41. Sacrificial layer 50can also be referred to as a protective layer in that sacrificial layer50 protects a portion of mass 44 from exposure to etching conditions,and protects mass 44 from debris associated with subsequent etchingand/or polishing conditions.

FIG. 3 illustrates wafer fragment 10 after the fragment has been exposedto chemical-mechanical polishing and/or etching. Such polishing and/oretching removes mass 44 from over upper surface 41 of insulativematerial 40. The polish and/or etch can also remove some of insulativematerial 40 to reduce a height of upper surface 41. Dry or wet etchingconditions can be used for removing mass 44 from over surface 41.

In the shown embodiment in which upper surface 52 of sacrificial layer50 is provided beneath upper surface 41 of mass 40, the polish and/oretch can remove some of material 44 from within opening 42 to leave arecessed upper surface 53 of material 44 within opening 42. In otherembodiments (not shown) in which sacrificial mass 50 has an uppersurface coextensive with upper surface 41, or above upper surface 41,mass 44 would typically not have a recessed upper surface within opening42.

Referring to FIG. 4, a nitrogen-containing mass 60 is formed over uppersurface 41 of silicon oxide-containing mass 40. Nitrogen-containing mass60 can comprise, for example, silicon nitride, and can be formed bychemical vapor deposition (CVD), preferably by plasma enhanced CVD(PECVD). The CVD preferably comprises a temperature of less than orequal to 200° C., and a pressure of from about 1 Torr to about 10 Torr.The CVD conditions can be utilized to deposit less than or equal toabout 200 Å of silicon nitride over silicon oxide-containing mass 40,and preferably are utilized to deposit from about 20 Å to about 30 Å ofsilicon nitride on silicon oxide-containing mass 40. In the shownembodiment, nitrogen-containing mass 60 extends across surface 52 ofsacrificial material 50, as well as across recessed upper surfaces 53 ofsilicon-containing mass 44. If sacrificial mass 50 comprisesphotoresist, then the material will be a porous material, andaccordingly the portion of nitrogen-containing mass 60 over material 50can also be relatively porous. Such portion can thus be removedutilizing typical conditions for stripping photoresist material 50 fromwithin opening 42.

Referring to FIG. 5, sacrificial mass 50 (FIG. 4), is removed fromwithin opening 42. Such leaves nitrogen-containing mass 60 over siliconoxide-containing mass 40, and over upper regions 53 ofsilicon-containing mass 44. However, nitrogen-containing mass 60 doesnot extend across a predominant portion of the surface 46 ofsilicon-containing mass 44.

A nitrogen-containing layer 62 is shown formed over surface 46 ofsilicon-containing material 44. Nitrogen-containing layer 62 cancomprise, for example, silicon nitride, and can be formed by exposingsilicon-containing mass 44 to ammonia under the conditions describedpreviously with respect to FIG. 1. Such exposure can, as described withrespect to FIG. 1, remove native oxide from over surface 46, and form aprotective silicon nitride material (shown as layer 62) over surface 46.Layer 62 can be considered a nitrogen-comprising mass formed acrosssilicon-containing material 44, and not across silicon oxide-containingmaterial 40. Specifically, the exposure of fragment 10 to ammonia willselectively form silicon nitride from the exposed silicon-containingsurface 46, but would not form any significant amount of silicon nitridefrom exposed surfaces of the silicon nitride material 60 already presentover silicon oxide-containing mass 40. The exposure to ammonia andformation of layer 62 shown at the processing step of FIG. 5 willtypically be omitted if such exposure and nitride layer formationoccurred at the FIG. 1 processing step. Generally, the particularprocessing steps in which it can be most suitable to expose asilicon-containing material to ammonia are during or after formation oflayer 44 and before formation of layer 66.

Referring to FIG. 6, a silicon nitride layer 66 is deposited oversilicon nitride materials 60 and 62. Silicon nitride layer 66 can be athermally formed nitride, or can be deposited by, for example, lowpressure chemical vapor deposition utilizing a temperature of less thanor equal to 750° C., and a pressure of from about 20 mTorr to about 2Torr. Layer 66 can be deposited to a thickness of less than or equal toabout 100 Å, and preferably is deposited to a thickness of from about 40Å to about 50 Å. Layer 66 can consist of, or consist essentially ofsilicon nitride.

It is noted that material 62 is an optional layer in the embodiment ofFIG. 6, and that the invention also encompasses embodiments whereinlayer 66 is chemical vapor deposited directly onto silicon-containingmass 44 while being deposited onto silicon nitride mass 60. Regardless,it is to be understood that silicon nitride layer 66 is deposited acrosssilicon oxide-containing mass 40 while being simultaneously depositedacross silicon-containing mass 44, and grows at about the same rate overboth silicon oxide-containing mass 40 and silicon-containing mass 44.

Ultimately, silicon nitride layers 60 and 66 together comprise a barrierlayer over silicon oxide-containing mass 40, and layers 62 and 66together define a dielectric material over silicon-containing mass 44.The dielectric material extending across silicon-containing mass 44 canfurther comprise an oxide layer (not shown) if a native oxide remainsbetween silicon-containing mass 44 and the deposited silicon nitridelayer 66. Such silicon dioxide layer is likely to result in embodimentsin which nitrogen-comprising layer 62 is omitted.

Each of layers 60, 62 and 66 can be referred to as a nitrogen-comprisingmass, and each of the layers can consist of, or consist essentially ofsilicon nitride. In particular terminology of the present invention,layer 60 can be referred to as a first nitrogen-containing mass, layer66 as a second nitrogen-containing mass, and layer 62 as an optionalthird nitrogen-containing mass.

FIG. 7 illustrates a capacitor construction 80 comprising the materialsof the FIG. 6 construction. Capacitor construction 80 is formed bydepositing a layer 82 of dielectric material over the silicon nitridelayer 66. Layer 82 can comprise, for example, silicon dioxide. Ofcourse, since silicon nitride layer 66 is itself a dielectric material,the invention also encompasses embodiments wherein layer 82 is omitted.In such embodiments, silicon nitride comprised by one or more of layers66 and 62 can be the only dielectric material in the capacitorconstruction.

A conductive capacitor electrode 84 is formed over dielectric material82. Conductive electrode 84 can comprise, for example, conductivelydoped polycrystalline silicon. In the capacitor construction 80, thesilicon-containing material 44 is a conductively-doped material thatdefines a first capacitor electrode of the capacitor construction.Further, dielectric materials 62, 66 and 82 define a dielectric regionof the capacitor that separates first electrode 44 from second electrode84. Capacitor construction 80 can be incorporated into a DRAM device. Inthe shown embodiment, source/drain region 18 is electrically connectedto a bit line 90.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

1. A method of forming a nitrogen containing mass, comprising: providinga monocrystalline silicon substrate, the substrate supporting asilicon-containing mass and a silicon oxide-containing mass; thesilicon-containing mass having substantially no oxygen therein; forminga first nitrogen-containing mass to be across the siliconoxide-containing mass and not across at least some of thesilicon-containing mass; and after forming the first nitrogen-containingmass, forming a second nitrogen-containing mass which extends across atleast some of the silicon-containing mass and across at least some ofthe silicon oxide-containing mass; the second nitrogen-containing massbeing over and in physical contact with the first nitrogen-containingmass.
 2. The method of claim 1 wherein the first nitrogen-containingmass is across at least a portion of the silicon-containing mass.
 3. Themethod of claim 1 wherein the silicon-containing mass consistsessentially of silicon.
 4. The method of claim 1 wherein thesilicon-containing mass consists essentially of conductively-dopedsilicon.
 5. The method of claim 1 wherein the silicon-containing massconsists of conductively-doped silicon.
 6. The method of claim 1 whereinthe silicon-containing mass comprises polycrystalline silicon.
 7. Themethod of claim 1 wherein the silicon-containing mass compriseshemispherical grain polycrystalline silicon.
 8. The method of claim 1wherein the silicon oxide-containing mass comprises borophosphosilicateglass.
 9. The method of claim 1 wherein the first nitrogen-containingmass comprises silicon nitride.
 10. The method of claim 1 wherein thesecond nitrogen-containing mass comprises silicon nitride.
 11. A methodof forming a silicon nitride layer, comprising: providing a firststructure comprising non-oxidized silicon and a second structurecomprising an oxide of silicon; forming a sacrificial layer over thefirst structure; while the sacrificial layer is over the firststructure, forming a nitrogen-containing material across at least someof the second structure; after forming the nitrogen-containing material,removing the sacrificial layer; and after removing the sacrificiallayer, forming a silicon nitride layer which extends across the firststructure and across the nitrogen-containing material.
 12. The method ofclaim 11 wherein the non-oxidized silicon comprises polycrystallinesilicon.
 13. The method of claim 11 wherein the non-oxidized siliconcomprises hemispherical grain polycrystalline silicon.
 14. The method ofclaim 11 wherein the oxide of silicon is comprised byborophosphosilicate glass.
 15. The method of claim 11 wherein thenitrogen-containing layer is silicon nitride.
 16. The method of claim 11wherein the sacrificial layer is photoresist.
 17. A method of forming asilicon nitride layer, comprising: providing a first structurecomprising silicon and a second structure comprising an oxide ofsilicon; forming photoresist over and in contact with the firststructure; while the photoresist is over the first structure, forming anitrogen-containing material across the second structure; after formingthe nitrogen-containing material, removing the photoresist; afterremoving the photoresist, forming a silicon nitride layer which extendsacross the first and second structures, the silicon nitride layer beingover the nitrogen-containing material; and conductively-doping the firststructure.
 18. The method of claim 17 wherein the conductively-doping ofthe first structure occurs prior to forming the silicon nitridematerial.
 19. The method of claim 17 wherein the first structurecomprises hemispherical grain polycrystalline silicon.
 20. A method offorming a capacitor construction, comprising: providing a substrate, thesubstrate comprising a first mass and a second mass, the first masscomprising silicon and the second mass comprising silicon oxide; formingphotoresist over and in contact with the first mass; while thephotoresist is over the first mass, forming a nitrogen-containingmaterial across at least a portion of the second mass; after forming thenitrogen-containing material, removing the photoresist; after removingthe photoresist, forming a silicon nitride layer which extends acrossthe first and second masses, the silicon nitride layer being over thenitrogen-containing material; conductively-doping the first mass todefine a first capacitor electrode; and forming a second capacitorelectrode spaced from the first capacitor electrode by at least thesilicon nitride layer; the silicon nitride layer, first capacitorelectrode and second capacitor electrode together defining at least aportion of a capacitor construction.
 21. The method of claim 20 furthercomprising forming a silicon oxide layer over the silicon nitride layerprior to forming the second capacitor electrode; the second capacitorelectrode being spaced from the first capacitor electrode by both thesilicon nitride layer and the silicon oxide layer.
 22. The method ofclaim 20 wherein the conductively-doping of the first mass occurs priorto forming the nitrogen-containing material.
 23. The method of claim 20wherein the first mass comprises hemispherical grain polycrystallinesilicon, and wherein the second mass comprises borophosphosilicateglass.